Much documentation exists about the causal relationship between immune complexes and the pathogenesis of glomerulonephritis and vasculitis in naturally occurring and experimentally induced immune complex disease. Immune complexes may also play an important role in mediating changes in the central nervous systems (CNS). Immune complex deposition in the choroid plexus, an organ with functional and structural similarities to the renal glomerulus, has been shown to occur during acute immune complex disease in the rabbit. Evidence suggests that the permeability of the blood: cerebrospinal fluid (CSF) barrier is compromised in association with the deposition of immune complexes in the choroid plexus. Furthermore, antigen, antibody and in some cases, immune complexes within the CSF, parallel their occurrence in the systemic circulation. The purpose of the proposed investigation is to examine the neuropathological and neurophysiological consequences occurring in the CNS during experimentally induced immune complex disease. Specifically, we will examine morphological and functional aspects of the brain and choroid plexus and relate these to the deposition of immune complexes in the CNS during immune complex disease. Factors which contribute to the deposition of immune complexes in the CNS will also be examined. An additional study will determine if the deposition of immune complexes in the CNS is a necessary condition, or facilitates the diffusion of CNS reactive antibodies from the circulation into the brain. Hopefully, these studies will also contribute to a better understanding of the neuropsychiatric manifestations in disorders such as systemic lupus erythematosus, as well as elaborating potential mechanisms whereby the immune system could alter CNS functioning.